added helper to avoid try/catch blocks

it seems try/catch blocks are slow in V8 (i.e. node.js).
I added them just to prevent futures from throwing exceptions
at me. This works fine, too.

Bonus: Made error handling a bit simpler in some places.
added check for internet connection
improved error messages of checkUpdateAssistant
Merge pull request #11 from webOS-ports/garfonso/work

added tests for internet connectivity and some cosmetic stuff